Food casings based on cellulose, and particularly fibrous food casings, have been used for decades for the production of raw sausages, dry sausages and semi-dry sausages.
In the manufacture of processed sausage products, a meat emulsion is prepared from comminuted meat together with fillers, seasonings, spices, etc. A tubular food casing, such as one containing non-edible cellulose, is loaded onto the stuffing horn of a filling machine and stuffed with the meat emulsion. In the case of small sausage products, the filled casings are twisted, tied or clipped into suitable links at predetermined intervals and further processed. For larger sausage products like bologna, salami, and the like, the meat emulsion is introduced into larger, heavier walled casings or casings having fibrous reinforcements, and formed into chubs or lengthy individual sausage sticks or logs for further processing, e.g. cooking and smoking.
Dry or semi-dry sausages, sometimes referred to as cervelats or summer sausages, are larger meat products, which include such representative examples as air dried pepperoni, soft salami, hard salami and dry salami, and the like. As the name suggests, this type of sausage has reduced moisture content, and its preparation usually includes drying as one step in its manufacture. Dry sausage may also be smoked. Cooking can also be performed in some instances during the smoking step.
Some of the typical features relating to these sausages and their production are presented in the following. First of all, there are significant variations in the meat emulsion compositions, which affect the processing and the final product. Further, filling or stuffing of the meat emulsion into casings ranges from close diameter control to manual highly varying diameter stuffing, and subsequent processing or curing of sausages ranges from fermented mild early cook to initial higher temperature cured raw sausage. There are also variations in the ripening and respective drying cycles to reach a final protein to fat ratio. Ripening and drying is characterized by a typical weight loss ranging from approximately 10 to 30%, which is associated with a volume proportional to the weight loss or moisture loss, mainly radial shrinkage.
Due to the above reasons several challenges and limitations are faced during the production of dry and semi-dry sausages. It is essential that the drying and ripening rate is such that no case hardening and mould formation takes place, both being temperature and relative humidity dependent. During the above mentioned production cycles the casing needs to adhere sufficiently to the sausage or meat mass to avoid grease or oil spot formation between the sausage and casing, and to prevent casing releasing. Further, the adhesion of the meat to the casing needs to be such that the casing can be peeled off by different peeling procedures, which may range from manual peeling to fast speed automatic peeling. Finally, the productivity should also be maintained at an acceptable level for economic reasons.
Several methods and chemical agents have been proposed for improving or creating adhesion of a cellulose casing to proteins or sausages and to ensure release of the casing.
However, these approaches have several limitations, for example the variation due to internal bubble coating technology, the fluctuation due to the variation in the amount of fibre on inside of the casing depending on the degree of viscose penetration, and too high adhesion particularly for sausage types requiring the combination of higher weight loss and fast or automatic peeling.
The internal bubble technique has several short-comings. The bubble method is dependent on many process variables making it difficult to achieve product uniformity and quality control. This is due to such variables as rate of casing travel; initial concentration of the coating solution; rate of exhaustion and depletion of resin from the coating solution; amount of pressure applied by the squeeze rolls, etc. Such factors determine the amount of resin with which the inner wall of the casing will be coated and the frequency with which the coating composition will require replenishing. Liquid transfer from tanks can also dilute the bubble in standard operations. Because the resin in solution between the rolls is constantly being depleted from the casing interior the coating being applied lacks uniformity and produces a “two side effect”, i.e., different meat cling over the circumference of the casing. Due to risks of roping or folding the coating via the bubble method can also result in uneven distribution and areas with insufficient active material.
The use of internal impregnation with combinations of chemicals including both an adhesion promoter chemical and a release chemical has been suggested in the art. The downsides and limitations of these approaches are for example the incompatibility of the different chemical families (hydrophobic versus hydrophilic) requiring additional components to act as emulsifiers, and difficulties in finding an acceptable balance between the chemicals and desired characteristics. The proposed solutions are typically only limited for a unique combination of sausage emulsion and processing and still have the variation associated with a typical internal bubble impregnation process.
In later developed double viscose coating technique adhesion promoters, such as polyamine-polyamide-epichlorohydrin resins, optionally in combination with proteins were incorporated into the internal cellulose layer of the double coated fibrous casings, whereby the elimination of the internal bubble impregnation variation was avoided, resulting in a more consistent internal cling ie. meat adhesion property.
More efficient and faster processing of food products, particularly pork and pepperoni sausages requires the use of higher production temperatures, which results in significant greasing out.
In order to meet the various challenges relating to food casings and their manufacture different approaches have been suggested, which may be optimum for a particular type of sausages but to this point each of these have shown limitations in both “general purpose use” and “sausage productivity enhancement”. None of the above described solutions are able to combat this problem in an optimal way and varying of the parameters typically leads to new problems.
In particular, there is a need for more efficient methods of preparing fibrous casings with desired balance between low cling (adhesion) properties where such properties can be replicated with better quality control and uniformity between production runs through less manual handling (bubble changes), automatic dosing of the adhering agent, and more consistent amounts of adhering agent being applied. There is further a need for being able to fine-tune adherence characteristics for various food casing products, which are similar under both wet and dry conditions, and also to decrease the amount of adhesion promoters and release compounds used in casings.
In the light of the state of the art it can be seen that there is a need for food casings and particularly for modified fibrous type food casings for dry and semi-dry sausage products, which offer a better balance between adherence/cling and release properties, meets the above requirements and simultaneously provides an economic solution with respect to sausage productivity.